C#实现Http请求的多种方案

// get 请求示例
async task<string> getdataasync(string url)
{
    using var httpclient = new httpclient();
    httpresponsemessage response = await httpclient.getasync(url);
    response.ensuresuccessstatuscode();
    return await response.content.readasstringasync();
}
 
// post 请求示例
async task postdataasync(string url, object data)
{
    using var httpclient = new httpclient();
    var json = jsonserializer.serialize(data);
    var content = new stringcontent(json, encoding.utf8, "application/json");
    var response = await httpclient.postasync(url, content);
    response.ensuresuccessstatuscode();
}

// 1. startup 注册服务
services.addhttpclient("financeapi", client => {
    client.baseaddress = new uri("https://api.finance.com");
    client.timeout = timespan.fromseconds(15);
    client.defaultrequestheaders.add("accept", "application/json");
});
 
// 2. 控制器中使用
public class datacontroller : controller
{
    private readonly ihttpclientfactory _factory;
    
    public datacontroller(ihttpclientfactory factory) => _factory = factory;
 
    public async task<iactionresult> getstockdata()
    {
        var client = _factory.createclient("financeapi");
        var response = await client.getasync("/stocks/msft");
        // ...
    }
}

var handler = new socketshttphandler
{
    pooledconnectionlifetime = timespan.fromminutes(5),
    enablemultiplehttp2connections = true
};
 
var client = new httpclient(handler)
{
    defaultrequestversion = httpversion.version20,
    defaultversionpolicy = httpversionpolicy.requestversionexact
};

// 避免大响应阻塞内存
async task processlargeresponse(string url)
{
    using var client = new httpclient();
    using var response = await client.getasync(url, httpcompletionoption.responseheadersread);
    using var stream = await response.content.readasstreamasync();
    
    await using var buffer = new bufferedstream(stream);
    using var reader = new streamreader(buffer);
    
    while (!reader.endofstream)
    {
        var line = await reader.readlineasync();
        processline(line);  // 逐行处理
    }
}

// 指数退避重试器
async task<t> executewithretry<t>(func<task<t>> action, int maxretries = 3)
{
    int retrycount = 0;
    while (true)
    {
        try
        {
            return await action();
        }
        catch (httprequestexception ex) when (ex.statuscode == httpstatuscode.toomanyrequests)
        {
            if (retrycount++ >= maxretries) throw;
            var delay = timespan.fromseconds(math.pow(2, retrycount));
            await task.delay(delay);
        }
    }
}
 
// 使用示例
var data = await executewithretry(() => getdataasync("https://unstable-api.com/data"));

// 安全 api 调用签名
async task sendsignedrequest(string url)
{
    var handler = new customsignaturehandler();
    var client = new httpclient(handler);
    // ... 正常调用
}
 
class customsignaturehandler : delegatinghandler
{
    protected override async task<httpresponsemessage> sendasync(
        httprequestmessage request,
        cancellationtoken canceltoken)
    {
        // 1. 获取时间戳
        var timestamp = datetimeoffset.utcnow.tounixtimemilliseconds();
        
        // 2. 生成签名
        var signdata = $"{request.method}{request.requesturi}{timestamp}{api_secret}";
        var signature = hmacsha256.hash(signdata);
        
        // 3. 添加安全头
        request.headers.add("x-timestamp", timestamp.tostring());
        request.headers.add("x-signature", convert.tobase64string(signature));
        
        return await base.sendasync(request, canceltoken);
    }
}

// 高效 json 反序列化
async task<t> parsejsonresponse<t>(httpresponsemessage response)
{
    // 使用流式 api 避免大对象分配
    await using var stream = await response.content.readasstreamasync();
    return await jsonserializer.deserializeasync<t>(stream, new jsonserializeroptions
    {
        propertynamecaseinsensitive = true,
        defaultbuffersize = 8192  // 8kb 缓冲区
    });
}
 
// 使用 arraypool 处理二进制响应
async task processbinaryresponse(string url)
{
    var response = await _httpclient.getasync(url);
    var buffer = arraypool<byte>.shared.rent(1024 * 64);
    
    try
    {
        await using var stream = await response.content.readasstreamasync();
        int bytesread;
        while ((bytesread = await stream.readasync(buffer)) > 0)
        {
            processchunk(new readonlyspan<byte>(buffer, 0, bytesread));
        }
    }
    finally
    {
        arraypool<byte>.shared.return(buffer);
    }
}

// 强制刷新 dns 缓存
var handler = new socketshttphandler
{
    pooledconnectionlifetime = timespan.fromminutes(5),  // 设置连接生命周期
    pooledconnectionidletimeout = timespan.fromseconds(30)
};

// 开发环境忽略证书错误（生产环境禁用！）
var handler = new httpclienthandler
{
    servercertificatecustomvalidationcallback = (_, _, _, _) => true
};

async task uploadfile(string url, string filepath)
{
    using var content = new multipartformdatacontent();
    using var filestream = file.openread(filepath);
    
    content.add(new streamcontent(filestream), "file", "data.zip");
    content.add(new stringcontent("2024-report"), "description");
    
    var response = await _httpclient.postasync(url, content);
    response.ensuresuccessstatuscode();
}

# 查看连接池状态
dotnet-counters monitor -n myapp system.net.http

// 添加日志记录器
services.addhttpclient("loggingclient")
    .configureprimaryhttpmessagehandler(() => new logginghandler(new socketshttphandler()));
 
class logginghandler : delegatinghandler
{
    protected override async task<httpresponsemessage> sendasync(
        httprequestmessage request, cancellationtoken cancellationtoken)
    {
        var stopwatch = stopwatch.startnew();
        try 
        {
            return await base.sendasync(request, cancellationtoken);
        }
        finally
        {
            _logger.loginformation($"{request.method} {request.requesturi} took {stopwatch.elapsedmilliseconds}ms");
        }
    }
}